In recent years, the development of inverted two-wheel vehicles that travel while maintaining the inverted state has been under way. Because of their characteristic feature that they need to maintain the inverted state, it is important to determine the getting-on/off of the rider in consideration of the safety and the like. For example, a getting-on/off determination apparatus that determines rider's getting-on/off for an inverted two-wheel vehicle by using a contact-type mechanical switch disposed in the step portion on which the rider stands has been known. This getting-on/off determination apparatus could suffer a durability problem because electric contacts of the mechanical switch are repeatedly brought into a contacted state and an un-contacted state every time a rider gets on/off the inverted two-wheel vehicle.
Further, to solve the problem like this, an inverted two-wheel vehicle using a noncontact-type optical switch in which when the step portion on which the rider stands is displaced downward, a detection light emitted from a light-emitting unit is blocked by the stem of the step portion and the getting-on/off of the rider is determined by detecting the interception of the detection light by using a detection unit has been known (see Patent literature 1).